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Frequently Asked Questions (FAQ)
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Yes, this is possible with RFEM and the RF-CONCRETE Members + RF-CONCRETE NL add-on module. For RSTAB, you need the CONCRETE add-on module.
You can define an "existing basic reinforcement" in the two add-on modules for RFEM and RSTAB and perform a nonlinear design at the ultimate limit state for this reinforcement.
As a result, you obtain the utilization ratio from the nonlinear calculation assuming the provided longitudinal reinforcement.
The nonlinear design is already included in the CONCRETE for RSTAB add-on module. In RFEM, the RF-CONCRETE NL add-on module is required.
In RF‑CONCRETE Surfaces, the compression reinforcement is calculated as well.
The note "compression reinforcement" is displayed in the design details for the respective reinforcement layer.
AnswerThe partial safety factors for reinforced concrete design can be edited in Window 1.6 "Reinforcement" in the corresponding tab for the selected National Annex (for example, DIN EN 1992‑1‑1).If required, you can also reset these values to the default value.In a similar way, this also applies to the add-on modules RF‑CONCRETE Surfaces and RF‑/CONCRETE Columns.
The RF‑CONCRETE Columns add-on module allows you to define a "creep-producing permanent load." You can find the corresponding tab in Window "1.1 General Data."
The reason for the entry is that RF‑CONCRETE Columns can apply this "creep-producing permanent load" for the automatic determination of the effective creep ratio according to EN 1992‑1‑1, 5.8.4.
In contrast, there is no explicit input option for this creep-producing permanent load in RF‑CONCRETE Members. In RF‑CONCRETE Members, the stability analysis of reinforced concrete columns by means of nonlinear design does not automatically reduce the effective creep ratio. You can find the background to the effective creep ratio applied in RF‑CONCRETE Members in Chapter 2.4.6 of the RF-CONCRETE Members manual.
The same applies to the CONCRETE Columns or CONCRETE add-on modules for RSTAB.
In the case of cross-section design, RF‑CONCRETE Members or CONCRETE uses in the calculation the stress-strain diagram for reinforcing steel according to DIN EN 1992‑1‑1, 3.2.7(2)a, that is, the increasing upper part up to ftk and the strain limitation of εud = 0.025.
In RF‑CONCRETE Members or CONCRETE, there is no option to switch to the design with the horizontal part according to 3.2.7(2)b.
However, you can possibly use a user-defined material with ftk = fyk.
After the calculation, you can switch to the result window "2.4 Required Reinforcement by x‑Location" in the RF‑CONCRETE Members (RFEM) or CONCRETE (RSTAB) add-on module.
Here, you can select a certain result row for a particular design and x-location (upper table in Window 2.4). Then, you can evaluate the intermediate results in the lower table in Window 2.4. This covers the "Neutral Axis Depth x", for example. The location of the neutral axis for the selected design location is displayed in the graphic on the right of Window 2.4 .
Furthermore, you can display the distribution of the neutral axis depth along the member length graphically in the model or in "Result Diagrams on Member."
You can find the setting in Window 1.5 Support.
Here, you can enter the support width and type, and specify whether to carry out the moment redistribution, or the reduction of moments or shear forces.
Depending on the standard selected in Window 1.1, there are different options available. The option applies to RF‑CONCRETE Members (RFEM 5) and CONCRETE (RSTAB 8).
Yes, it does, because this affects the stiffness of the entire structure.
When entering a flush beam as a "Rib," you will add the stiffness of the defined rectangular cross-section to the area of the line.
However, you have to only define the integration width for the result beam. The entered rectangular cross-section does not affect the stiffness of the entire structure, but is only applied as a design cross-section in the add-on modules (for example, RF‑CONCRETE Members).
AnswerA non-designable situation like this is displayed if the shear resistance without shear reinforcement VRd,c is arithmetically smaller than zero.The value for VRd,c of less than zero is caused by large tensile axial forces. In this context, the cross-section is completely under tension or completely cracked, and no shear force resistance can be created.For coated cross-sections with planned shear reinforcement, the following situation results:If VRd,c < 0, no further shear design is performed in RF‑CONCRETE Surfaces, and Note 13) is displayed. This approach is conservative.In this context, there was a request (194) for the interpretation of the standard, which allows the truss model to be used even with a completely cracked cross-section.If a shear reinforcement is designed as planned, you can ignore the message about the non-designable situation in the program. In this case, you should ensure that VEd is smaller than VRd,max and VRd,s.
You can connect a rib member to a line on two surfaces with different thicknesses.
To determine the stiffness or internal forces, the eccentricity of the rectangular cross-section is determined by using the mean value of both connected surfaces in RFEM.
For design in RF‑CONCRETE Members, the add-on module determines a special cross-section, which is displayed in Window "1.4 Ribs" of the add-on module.
By clicking the "i" button (see Figure 02), it is possible to open an info dialog box for the generated rib cross-section, where you can see all cross-section properties applied for the design in the add-on module, such as the position of the shear center and center of gravity, and so on.
If adjusting the "effective width" in Window "1.4 Ribs" (for example, to 0.50 m), this has an impact on the cross-section applied in RF‑CONCRETE Members and the cross-section properties of it.
However, this does not affect the stiffness or the determination of internal forces in the 3D model in RFEM.
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Wind Simulation & Wind Load Generation
With the stand-alone program RWIND Simulation, wind flows around simple or complex structures can be simulated by means of a digital wind tunnel.
The generated wind loads acting on these objects can be imported to RFEM or RSTAB.
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